Carbon seals generally may be used to seal a fluid leakage path between a static component and a rotating component, for example in a gas turbine engine for sealing oil within a gearbox. Carbon seals may be either contacting or air riding, and generally may include a stator fixed and sealed to the static component, and a rotor fixed and sealed to the rotating component. A carbon ring may be mounted axially between the stator and the rotor with a spring to force the carbon into contact or proximity with the rotor.
In an air riding carbon seal, the rotor may be designed with hydropads, which cause separation of the carbon ring and the rotor with a fluid (air) film. The design of an air riding carbon seal and the hydropads may be dependent on such factors and parameters as rotational speed of the rotating component, force of the spring loading the carbon ring against the rotor, and pressure differential across the seal. If an air riding carbon seal is operated outside its design point (range), it may leak or become, effectively, a contacting face seal. Common air riding carbon seals are generally designed for a specific range of load conditions, i.e., lower pressure differential across the seal, and therefore may not be as effective with load conditions outside of that range.
Therefore, it would be helpful to provide a carbon seal, such as an air riding carbon seal, that may accommodate a wide range of design conditions, such as differences in pressure differential and speed.